Albumin to prealbumin ratio in peritoneal dialysis patients: Clinical implication and outcome prediction

Abstract

Background: Serum prealbumin level is slightly higher, whereas albumin is lower in peritoneal dialysis (PD) than hemodialysis (HD) patients. It is unknown whether albumin to prealbumin ratio (APR) is associated with mortality risk among PD patients. This study aimed to evaluate the clinical implications of APR and its prediction value on long-term outcomes of PD patients.

Methods: The study population were prevalent PD patients at a tertiary hospital. Based on APR, a total of 220 PD patients were divided into 3 groups: group 1: top tertile, median APR: 121.1; IQR:109.5-131.9 (n = 73, male: 37%; age: 59±13); group 2: middle tertile, median APR: 97.1; IQR 93.5-100.0 (n = 73, male:37%; age: 54±14), and group3: bottom tertile, median APR: 81.3; IQR:76.8-85.0 (n = 74, male:38%; 54±11). Patients were followed up for a maximum of 5 years. Outcome of interest was all-cause mortality.

Results: Group 1 was characterized by older age, higher prevalence of diabetes, lower nPCR, higher Davies score and hs-CRP level. APR positively correlated to hs-CRP (β = 0.149, p = 0.045), but negatively correlated to nPCR (β = -0.161, p = 0.034). Hyperprealbuminemia, accounting for 0%, 23.3%, and 82.4% in groups 1,2, and 3, was associated with a lower risk for mortality (HR:0.41, 95%CI = 0.23-0.73). The cumulative survival is significantly lower in group 1 than the other two groups. By multivariable Cox regression, APR (HR:1.02; 95%CI:1.01-1.03) was found to be an independent predictor of long-term mortality.

Conclusion: PD patients with high APR are characterized by having more comorbidities and marked malnutrition-inflammation status, and are associated with long-term mortality, whereas hyperprealbuminemia and lower APR are favorable prognostic factors.

Fig 2. Hazard ratios of mortality stratified by prealbuminemia level.

As opposed to group 1 with normoprealbuminemia (reference), groups 2 and 3 lost their survival benefit in normoprealbuminemia panel. Whereas in hyperprealbuminemia panel, individuals in group 3 had significantly lower mortality risk than reference group, but group 2 with only 17 in patient number, did not show any difference compared to group 1.

Fig 1. Kaplan-Meier survival analysis of cumulative all-cause mortality among three groups of patients based on tertile of albumin to prealbumin ratio.

After 5 years’ follow-up, group 1 had lower cumulative survival rate than the other two groups (i.e., groups 2 and 3). There was no survival difference between groups 2 and 3.

Fig 3. Receiver operating characteristic (ROC) curves of prealbumin, albumin and reciprocal of APR (1/APR).

AUC value (0.708) of prealbumin was larger than either 1/APR (0.664) or albumin (0.651). The optimal cut-off of ROC in prealbumin was 33.5 mg/dL.